A solar cell or photovoltaic cell is a device that converts sunlight into electricity. This conversion is done by the photovoltaic effect. Currently, there are many different types of solar cells; however, all solar cells require a light absorbing material contained within the cell structure to absorb photons and generate electrons via the photovoltaic effect. The light absorbing materials can often be used in multiple physical configurations to take advantage of different light absorption and charge separation mechanisms.
In most cases, photovoltaic or solar cells are made of either silicon or thin-film cells. The various thin-film technologies currently being developed reduce the amount (or mass) of light absorbing material required in creating a solar cell. This can lead to reduced processing costs from that of bulk materials (e.g., silicon thin films) and also reduced energy conversion efficiency (an average 7 to 10% efficiency). Thin film cells may be, for example, inorganic layers, organic dyes, and organic polymers that are deposited on supporting substrates. Another group of materials used for solar cells consist of nanocrystals (e.g., electron-confined nanoparticles) embedded in a supporting matrix.
First generation cells consist of large-area, high quality single-crystal, single junction devices. This generation of devices, though, involves high energy and labor costs which make them prohibitively expensive to manufacture. Also, single junction silicon devices are approaching their limits of efficiency. Second generation cells and methods of manufacturing have been designed to address energy requirements and production costs of solar cells. For example, alternative manufacturing techniques such as vapor deposition and electroplating techniques have been developed to reduce processing and labor costs. One of the more successful second generation cells, for example, uses cadmium telluride (CdTe), copper indium gallium selenide, amorphous silicon and micromorphous silicon. These materials are applied in a thin film to a supporting substrate such as glass or ceramics, which reduces material mass and therefore costs. Third generation technologies aim to enhance poor electrical performance of second generation (thin-film technologies) while maintaining very low production costs.
However, regardless of the generation, solar cells efficiency remains low due, in part, to the lack of available light being properly directed to the semiconductor surface of solar cells. And, currently, there are few practical approaches to achieving higher efficiencies in such devices.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.